The invention relates to space transportation and exploration vehicles and more particularly, to a space vehicle which may be employed to reliably and safely return crew members from an earth orbiting vehicle, such as a space station or the like, to the earth with a minimum of cost and on-orbit preparation.
2. Brief Description of the Related Art
Since the beginning of the manned space program, NASA has been concerned with an Assured Crew Return Capability (ACRC). During the Mercury and Gemini programs, the design of the first orbit's trajectory assured the return of the vehicle into the atmosphere. The early Apollo missions to the Moon were flown in a "free return" trajectory , where the vehicle could circle the Moon and return home automatically. The value of this philosophy was demonstrated when the Lunar Module was used as an emergency vehicle on the Apollo 13 Mission. The Skylab missions had an Apollo Command Module docked to it during manned occupancy. (A method also used by the Soviet Union in its MIR space station.) The Space Shuttle provides a high level of redundancy for critical systems for the same reason. Likewise, the Space Station Freedom is being designed today with provisions for ACRC.
The Space Station Freedom is being developed as a permanent, manned vehicle located in low Earth orbit (LEO). The Space Shuttle will be used to deliver Space Station Freedom elements to orbit and provide crew rotation and space station logistics. The cycle time for Space Shuttle deliveries to the manned Space Station Freedom is expected to be about 3 months.
Unlike previous manned space vehicles, the permanently orbiting facility will not inherently return the crew to earth. Consequently, a crew return module is being developed which would always be docked at the Space Station Freedom to assure return for the Space Station Freedom crew. At least three situations have been identified where such a return module is essential: (1) In a medical emergency, where a crew member suffers a severe injury or illness which exceeds the capability of the Space Station Freedom's medical facilities, and the Space Shuttle cycle time is inadequate. (2) Space Station Freedom catastrophe during a period when the Space Shuttle Orbiter is away from the station. (3) Space Shuttle program problems which might prevent a timely availability of the Space Shuttle.
The design philosophy for the return vehicle is to "keep it simple," which implies high reliability and low maintenance. Consistent with this philosophy, subsystems would be passive where appropriate and would be "off the shelf" items, implying no technology risk. The Space Station Freedom interfaces will be at a minimum, particularly in the areas of maintenance, state of health monitoring, training, and operations.
Mission time should be at a minimum consistent with flight safety rules and procedures. This will typically reduce the size, weight, and performance requirements of the subsystems. This also implies that it is acceptable to have "large" dispersions between the touchdown point and the desired target area.
Once the return vehicle is in the water, primary rescue will be performed by the world-wide search and rescue (SAR) forces. Since the rescue time could be on the order of a day, the qualities of the return vehicle's flotation dynamics will be maximized along with crew comfort requirements that are consistent with crew safety. It should be noted that these design assumptions do not address the medical requirement of having available imminent hospital care for an injured crewmember, but emphasize the benchmark for simplicity.
The technology required to return people safely from orbit is not new and the ACRV is based on the heritage of prior entry spacecraft. Further, the ACRV has no "up" requirements and, as such, allows the design to have the freedom of increased simplicity. It is tempting in a design study of an ACRV for the Space Station Freedom, to focus on the active phase for such a system. However, the novel and most challenging design aspects of the ACRV lie in the quiescent phases of this system, particularly in being on the Space Station Freedom for an extended period of time yet always available for a safe, reliable return when needed. High reliability after an extended dormant period and minimum interface with the Space Station Freedom (and the associated maintenance, integration, logistics, and resupply) dictates a system which is as passive and simple as possible. The return vehicle concept described herein has addressed simplicity and passiveness through minimizing on-orbit loiter time and associated system requirements while providing an aerodynamically stable ballistic entry vehicle as well as a seaworthy craft. It is proposed that a simple ACRV such as the return vehicle can complement the Space Shuttle Transportation System by providing an assured crew return capability for all needs.
To successfully design such a system, a number of physical vehicle configuration requirements must be met. Delivery to the Space Station Freedom in the Orbiter payload bay demands that the vehicle diameter be less than 15 ft., that it be able to withstand Space Shuttle launch loads, and that it be compatible with Space Shuttle systems. A requirement for rapid ingress, checkout, and release must also be met in the event of an Space Station Freedom catastrophe. This requires acceptable thermal conditions for instantaneous use of all vehicle systems and crew compatibility in a shirtsleeve environment. Also, due to the extended crew on-orbit times, the training and proficiency required by the return vehicle for mission success must be minimized.
On-orbit and entry trajectory considerations also mandate a number of vehicle and system requirements. The vehicle must have the capability to deorbit from the Space Station Freedom and safely return the crew to Earth. A maximum free-flight time of 3 hours was imposed in an effort to have a completely passive environmental control and life support system (ECLSS) as well as reduce the power requirements of the vehicle. Crew physiological constraints limit the entry loading to 10 g's for less than 1 minute, and these loads can be over 3 g's for less than 5 minutes. Crew survival for both water and land landings will be met by providing impact attenuation in addition to the parachute system.
The minimum mission time and passivity of design imposed on the vehicle limits the amount of loiter time the vehicle can orbit the Earth in search of an opportune landing site. In turn, this limits the ability of the vehicle to always land near a rescue site. The imperative of this design was the reliable, safe return of the crew with simple, passive systems, which necessitates some compromise in accurate landing at choice sites. If the vehicle does land a large distance from a rescue site, the crew might have to wait for extended periods of time before being rescued. An assured buoyancy capability requires that the vehicle e a seaworthy craft. Basic survival necessities are also required along with a commercially available rescue beacon.
A brief description of some of the known related art follows:
Steadman U.S. Pat. No. 211,104 discloses the design of a toy having a shape somewhat similar to the instant invention.
Faget, et al, U.S. Pat. No. 3,093,346 discloses a space capsule having the capability to return humans to earth from earth orbit along a ballistic trajectory by use of retro-firing rockets. The patent teaches a capsule having a cylindrically- shaped portion, a conically-shaped portion and a heat shield
Schmidt U.S. Pat. No. 3,270,985 discloses a reaction control system in the context of a similarly shaped vehicle.
Paine U.S. Pat. No. 3,606,212 teaches an emergency rescue vehicle having some of the features of present invention.